Conversion of MSW into fuel

ABSTRACT

Utilization of a rotary drum composter to facilitate separation of a mixed municipal solid waste stream into combustible (food waste, paper, yard wastes, etc.) and combustible (plastic, rubber, wood, clothing, etc.) fractions and using the high BTU combustible fraction as a primary fuel, that can be supplemented with other combustible wastes such as Construction and demolition wastes and tires, for gasification to produce a usable and burnable gas for power production.

SUMMARY

The present invention relates to apparatus and a method of using a rotary drum composter such as the EWESON DIGESTER (U.S. Pat. No. 3,245,759 and U.S. Pat. No. 5,047,349) in combination with a closed loop gasification system such as described in U.S. Pat. No. 6,439,135 to prepare high BTU value fuel from a diverse mixed municipal waste stream by particalizing the compostable fraction through the physical and biological actions within the drum such that these two streams can then be readily separated by particle size using a trommel or flat screening device resulting in a high BTU value combustible fraction (mostly plastics, rubber, clothing, tires, wood, etc.) then to be gasified in a closed loop gasification system. The resultant gas can be used for power generation through steam production or electrical generating by means well known in the art.

DETAILED DESCRIPTION OF THE INVENTION

Gasification is a technology which uses heat and pressure to “gasify” combustible materials. There is no direct flame or burn. The combustible materials in this instance would come from a mixed municipal solid waste stream. Materials such as paper, cardboard, food waste, wood, tires, furniture, clothing and compost are all combustible. However, these materials in an as delivered form cannot be utilized in a gasifier. Time Consuming labor and mechanical equipment cost to size, separate and dry this disparate waste stream/fuel source is necessary. The use of a rotary drum composter (see FIG. 1) to pre-process MSW for fuel use provides a surprising and unexpected result by efficiently sizing, drying and homogenizing the waste stream and allowing for the ready removal of combustible fuel after the drum processing. The “fuel” produced can also be the raw compost, by itself which has a BTU value of at least 5000 per lb. in combination with what otherwise be screened away from the compost, i.e.—plastics, synthetics, clothing which are referred to as residuals and normally land filled BUT have a BTU value in excess of 10,000 BTU per lb. combining these two technologies provides an unexpected and efficient method of taking mixed waste and preparing it as a fuel and then utilizing the fuel to create power, either gas or electricity using an indirect combustor/gasification unit. The fuel material and the aeration action by use of forced air through the drum (see FIG. 1) facilitate the drying of the material being processed. The drum can be either open or partitioned. The speed of the rotation determines residence time. The MSW with or without biosolids is dried and sized and when discharged is able to be readily screened of metals and glass thus preparing an optimum fuel for gasification and thermal oxidation.

BRIEF DESCRIPTION OF DRAWING

The accompanying drawing depicts the configuration and use of the rotary composter to separate and prepare the fuel and the gasifier which converts the combustible material into a usable gas for power generation.

Fuel Preparation Drum

The fuel is prepared through the use of a horizontal rotary drum which is mounted on large bearings and turned through a bull gear or friction drive mechanism. Typically, drum sizes will be from 10′ to 20′ in diameter and 80′ to 300′ long. The drum facilitates mixing, aeration and material movement, and sizing of the material allowing separation.

Gasification and Thermal Oxidation

The prepared fuel is then processed through a multi-staged gasification process (see U.S. Pat. No. 6,439,135) which includes gasification and controlled oxidation resulting in an engine quality gas that can be used as is or burned in a gas turbine generator to create electricity. Temperatures achieved in the gasification and controlled oxidation process range from 500° F. to 3000° F. The gasification/oxidation process is performed within combustion chambers and boilers and efficiently turns processed “fuel” prepared by a rotary drum mixing/composting drum, such as municipal waste or any solid carbon based material, into clean usable energy. Gasification and partial oxidation take place in separate gasification and oxidation areas of a single chamber or multi-chamber and final complete combustion takes place in the boiler or engine.

Utilization of Gasification Produced Energy

The gas produced from the gasification process can be utilized to produce steam through a boiler system or can be directly used by a turbine generator to produce electricity (see FIG. 1). This power can be utilized by the composting facility itself as well as used and marketed publicly. 

1. A process for utilizing MSW as a fuel: which comprises rotary-drum composting the MSW to facilitate screen separation of combustibles and thermally gasifying the combustibles to produce a high energy stream for power generation. 